1. Field of Invention
The present invention relates to a light-emitting device, such as a liquid crystal device, an organic EL (electroluminescent) device or an inorganic EL device, a manufacturing method of the light-emitting device, and an electronic apparatus in which the light-emitting device is mounted.
2. Description of Related Art
Conventionally, in light-emitting devices such as organic electroluminescent (hereinafter, referred to as organic EL) devices, a plurality of circuit elements, an anode, a hole injection layer, a light-emitting layer made of an electro-optical material such as an EL material, a cathode and so on are deposited on a substrate, and then a sealing substrate is provided, with these elements interposed between the substrates. More specifically, an anode made of a transparent conductive material such as indium tin oxide (ITO) or tin oxide (SnO2), a hole injecting layer made of a dopant such as polythiophene derivative (hereinafter, referred to as PEDOT), a light-emitting layer made of a light-emitting material such as polyfluorene, and a cathode made of a metallic material having a low work function such as Ca or a metallic compound are sequentially deposited on a transparent substrate such as a glass substrate.
In such an organic EL device, holes injected from the anode side and electrons injected from the cathode side are recombined in the fluorescent light-emitting layer, and when the recombined holes and electrons relax from an excited state, light emission is caused.
Further, as a structure in which the light is emitted to a viewer side, for example, a so-called bottom-emission-type structure is known, in which the emitted light is emitted from the substrate side on which the circuit elements are formed (for example, see U.S. Pat. No. 4,356,429). Further, in recent years, demands for large organic EL devices having high definition and high brightness are increasing, and thus, top-emission-type organic EL devices, which are suitable for realizing light-emitting elements having high aperture ratio and high efficiency, are being studied and developed (for example, see International Publication Pamphlet No. WO98/36407).
In the top-emission-type organic EL device, an upper electrode in the light-emitting side is needed to be transparent, and in the construction described in U.S. Pat. No. 4,356,429, the upper electrode is comprised of an ITO (indium tin oxide) film or a thin laminate of an Al film and an ITO film. However, when such the construction is adopted, a transparent conductive film, typified by an ITO film, has high resistance as compared with a metallic film, typified by an Al film, and thus brightness irregularity of the light-emitting element is caused by a voltage drop due to the resistance of the transparent conductive film itself.
Further, if the upper electrode is formed with a metallic film such as Al, there is a problem in that sufficient transmittance is not obtained and the light emission efficiency is lowered.
Further, in almost all top-emission-type structures, the electrode is transparent, and thus sufficient transmittance is not obtained, or, even though transmittance is obtained, the reliability is poor. Further, in a conventional organic EL device, since the light emitted from the light-emitting layer is emitted directly outside, there is a problem in that light of not more than 20 percent is emitted.
Further, if the transparent conductive material made of a metallic oxide such as ITO is deposited on the electron injecting layer having a low work function including an alkali metallic material such as Li or Na or an alkali earth metallic material such as Be, Mg or Ca, the electron injecting layer may be damaged.
Meanwhile, in the bottom-emission-type organic EL device, since various wiring lines are arranged at positions which block emitted light, there is a problem in that the emission efficiency of light is lowered due to the wiring lines.